The Economist (2020-10-10):

2,500 years ago a small Greek fleet thrashed a huge Persian one. ...

It is the 2,500th anniversary of one of the greatest naval battles of the ancient world. In the early autumn of 480BC, in the strait between Salamis and the mainland, a few hundred Greek triremes (warships with three banks of oars and bronze battering-rams) defeated a much larger Persian armada.

However, there was no Year Zero. So, shouldn't

  1. 2,500 years ago be 481 BC?
  2. And 480 BC + 2500 years = AD 2021, so that the 2500th anniversary of this battle be AD 2021?
  • 4
    Possibly to avoid a clash with the 200th anniversary of the beginning of the Greek war of independence in 1821? Or perhaps simply because 2020 + 480 = 2,500 years = a nice bunch of round numbers so let's keep it like that as it's close enough. Or maybe someone boobed and it's too late to admit it. Maybe worth contacting the Greek Ministry of Culture? Oct 13, 2020 at 4:26
  • 5
    Obviously it should be 2021 but this isn't a history question - it's a political decision by the Greeks, which is a field (politics) notoriously not bound by historicity. One might speculate on the financial benefits to the sale of commemorative memorabilia..... BTW, not that it makes a difference since they both take place in 480 BC, but your title references Thermopylae but the body & quotes are talking about the Battle of Salamis?
    – Semaphore
    Oct 13, 2020 at 6:03
  • 2
    As it currently stands, this question is not a good fit for History.SE as it is more of a maths/politics question, and essentially a duplicate of this more generalized question: history.stackexchange.com/questions/47246/time-span-of-a-decade. Perhaps there could be a history question here (is there grounds to challenge the conventional dating of the battles?) but it would have to be edited.
    – Semaphore
    Oct 13, 2020 at 9:18
  • The ancients did not possess a concept of zero, which is why they used inclusive counting; this can still be seen, until this very day, within traditional Christian calendars, such as the Greek Orthodox one, wherein the Sunday following Easter, for instance, is called the second Sunday after, instead of the first; etc. Thus, the first anniversary being the event itself, as it were, according to this system of reckoning, its 2,500th commemoration does indeed fall within the current year, since, as you noted, there is no year zero.
    – Lucian
    Oct 13, 2020 at 14:40
  • @Lucian - the ancients did have a concept of zero, they just thought of it differently than we do. A zero on an abacus is ... what? Don't move a stone. Today is Sunday (1) next Sunday is 2.
    – Mayo
    Oct 13, 2020 at 14:49